Moxa is another name for the herb artemesia mugwort. Mugwort has been medicinally used in Chinese medicine for thousands of years in a process called moxibustion.
Simply put, moxa is burned over the body to help warm it during an acupuncture treatment. When moxa burns, it does not flame up but smolders slowly. (Think about a lit incense stick or a cigar). It gives off a very radiant warm heat that penetrates the body deeply and helps warm the qi as well as add energy to the body. Our qi, like all things in nature, responds to heat and cold. Cold qi tends to contract and stagnate. Warm qi tends to expand and to flow more smoothly. By using moxa we are able to build qi in the body and help it move easier. This is especially useful when a patient's pain is caused by not enough qi or when there is a lot of cold in the body.
Moxa can be used in many ways. Sometimes we will use a large roll of moxa that looks like a cigar which we will light and pass an inch or two over the pathway of a qi (called a meridian). Moxa can be placed in a moxa box which can warm a whole area (like an ancient heating pad or hot water bottle). Moxa rolls can be placed on acupuncture needles and lit. Most often, I place small mounds of moxa (rolled into cone shapes) directly onto an acupuncture point and light it with an incense stick. As soon as the patient feels the heat (or the mound burns halfway down) we remove that cone and repeat, taking great care to avoid discomfort or burning. Most patients find moxa treatments incredibly relaxing and nourishing and look forward to it--especially on cold winter days.